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I recently heard about Aeroflot flight 593 and I know the cause is pilot error or whatever you would like to call that, but I have a couple of question about the aircraft.

  1. First of all, I have never heard of part of the autopilot disconnecting. I have never heard of just the ailerons of the autopilot disconnecting, was this just a feature of the aircraft? Can any new Airbus or any modern day aircraft's autopilot partly disconnect to a system?

  2. Lastly I know the autopilot pitched up and increased thrust to gain altitude but why did it stall, why didn't the autopilot stop pitching the nose up and increasing thrust once it got to high and dangerous?

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The autopilot will disengage if the controls are manually manipulated while the autopilot is on. The main issue with this particular airplane was that there was no audible autopilot enunciation that indicated that the autopilot turned off which is what the pilots were used to hearing on Russian made jets. Rather there was only an indication light that would go on if autopilot disengaged and could go unnoticed. The autopilot disengagement was not noticed right away and the aircraft entered into a spiral spin. The pilots tried to recover from the spin but they pulled up too much (over corrected) and the plane entered a stall.

Autopilots can disengaged automatically for a number of reasons. For example Air France 447 autopilot disengaged due to conflicting information from the airspeed indicators. Incorrect actions by the pilots after the autopilot disengagement caused that accident. In modern day aircraft the autopilot disengagement is heard as an audible signal so the pilot knows to take over. If Aeroflot 593 had this feature the accident could have been avoided (besides not having your kids fly the airplane).

To answer your questions about he various levels of autopilots there is really only one autopilot that works in conjunction with other automated systems to fly the plane below is a description of the various systems:

Autopilot: Automatically flies the plane according to instruments. This system is responsible for manipulating the control column.

Auto-Thrust: Automatically adjust thrust to maintain a constant airspeed.

Yaw-Dampening: Automatically adjust rudders for coordinated turns. Yaw-Dampening can work when autopilot is on or when the airplane is manually flown.

Just because the autopilot disengages does not necessarily mean the other systems disengage.

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  • $\begingroup$ ok that makes sense, but what about the autopilot over pitching and for the thrust to increases once it reaches an unsafe level? $\endgroup$
    – Gary Zenger
    Commented Apr 27, 2018 at 18:33
  • $\begingroup$ The autopilot did not over pitch it was disengaged. The pilot over pitched which caused the stall. Also from the CVR transcript is looks like the pilot ordered more thrust and wasn't controlled by the auto-thrust. All the "autopilot" systems should disengaged when the aircraft enters an unusual attitude. $\endgroup$
    – DLH
    Commented Apr 27, 2018 at 18:41
  • $\begingroup$ You may be confusing autopilot with the flight protections of fly-by-wire aircraft. Fly-by-wire was not introduced until the A320 so no fly-by-wire protections were on this aircraft. $\endgroup$
    – DLH
    Commented Apr 27, 2018 at 18:43
  • $\begingroup$ I thinks so too, thanks for all your help :) $\endgroup$
    – Gary Zenger
    Commented Apr 27, 2018 at 19:38
  • $\begingroup$ so in the wikipedia site it says "The autopilot (which no longer controls the ailerons) used it's other controls in a bid to compensate, pitching the nose up, and increasing thrust. The plane begins go stall. The autopilot, unable to cope, disengages completely." So why didn't the autopilot stop once it got to a too high attitude? Would fly-by-wire system, which you said isn't on that plane have not allowed it to get to that attitude and it only got to that high of an attitude beucase it didn't have a fly-by-wire system? $\endgroup$
    – Gary Zenger
    Commented Apr 28, 2018 at 6:24

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